A PRIVATE investigator, foul-mouthed union members, security workers patrolling the streets and claims of intimidation from Glencore and the CFMEU have come out of the wash of an explosive Fair Work Commission hearing.

It would determine whether or not Glencore could punish more than 20 Oaky North workers for their behaviour at the picket line and online.

Transcripts reveal that during the three-day hearing in Emerald, the F-word was said 25 times, C-word 12 times, 'grub' 156, 'scab' 107 and 'maggot' 21.

Barrister for the CFMEU, Robert Reitano, was one of few people who didn't take offence to foul language, ignoring a "regrettable" remark towards him from a Glencore supervisor as the hearing centred around the behaviour of protesting workers.

A group of workers have been protesting against Glencore's proposed enterprise bargaining agreement since May.

Oaky North Picket Line on August 9:
Oaky North Picket Line on August 9

Outside the entrance to the mine the men have a picket line where they hold signs, play music and chant as people drive past.

Glencore locked the workers out of the mine on June 9 claiming the industrial action had cost the mining giant 6400 man hours and the workers haven't been allowed back in since.

The commission heard that Glencore contracted a security company to monitor their workers at the picket line, while in town at Tieri and on one occasion when there was a gathering at the local Girls Guide Hut.

The workers who gave evidence said they were aware of this surveillance, but then on June 15, when they voted down the proposed EA again, it was used against them.

On that day more than 20 workers were told by Glencore that their jobs were in jeopardy because of their actions at the picket line and on Facebook.

Glencore's barrister Christopher Murdoch maintained the timing was not punishment for the workers not agreeing to the EA but because it was the first time since they were locked out that they were allowed back on site.

To stop them losing their jobs the CFMEU called on the Fair Work Commission to step in, which resulted in the hearing in Emerald.

Mr Murdoch gave the commission examples of the behaviour the company took offence to, including people yelling at people leaving the mine, calling them a "grub", "F---ing grub" and "maggot".

A message for workers who haven't been locked out of Glencore's Oaky North Mine.Campbell Gellie

"Referring to (a manager) as a (C-word) in a Facebook page," he said. "Referring to another person as a dog and then making a statement, 'I know who you are and go for your life. Chew on this one you maggot', on the Facebook page."

Mr Murdoch claimed the behaviour was to intimidate those who continued to work at the mine during the protest and the contract workers who had replaced them.

But the commission heard not all contractors were intimidated.

Oaky North CFMEU lodge president Danny John Allen gave evidence to the commission that a ute load of contractors had been taunting them which provoked them to call the contractors grubs.

The retaliation from the protesters was caught on camera by Glencore's security guards.

CFMEU barrister Mr Reitano said Glencore used its investigation as "weaponry" to retaliate against the union workers after they voted down the proposed enterprise agreement. He said the letters had already been prepared on July 13.

Mr Reitano also said that it was no coincidence that on June 24 at 7.30am there was an email sent between Oaky Creek Security and a mine manager asking for the addresses of union members.

And then by 1pm an internal Glencore document stated that a private investigator would "collect intel on known addresses of possible union members and start creation of intel brief".

"Where you're going to surveil people, there's got to be some reasonable basis for it, and a reasonable basis isn't established here," Mr Reitano told the commission.

But a supervisor of the security company gave evidence that union members' addresses were not provided to them.

"The company's evidence is that it did not make a request for general surveillance and it did not provide the addresses," Mr Murdoch argued.

Fair Work Commission deputy president Ingris Asbury said she would try and release her decision as to whether Glencore could follow through with its disciplinary action against the workers as soon as possible.